LEDs are semiconductor devices that produce light when a current is supplied to them. LEDs are intrinsically DC devices that only pass current in one polarity, and historically have been driven by DC power supplies. When driven by DC power supplies, LEDs are typically provided in a string or parallel strings of LEDs which operate in the forward direction such that each LED is continuously operable. Once one LED within a string of LEDs burns out, the entire string will be rendered inoperable and the device containing the string may have to be replaced.
Recent advancements in the field of lighting have led to the use of LED circuits which are capable of using AC power to drive LEDs configured in particular circuit arrangements such that some of the LEDs operate during the positive phase of the AC power cycle and some LEDs operate during the negative phase of the AC power cycle. While this may extend the life of some LEDs within the circuit(s) as they will be turned on or off, flicker may become an issue as the voltage raises up and down, and the other known LED problems are realized.
Whether powered by AC or DC power sources, the amount of current flowing through an LED may dramatically affect the light output of and lifespan of the LED. This is because LEDs emit light based on the amount of current passing through them—the more current that passes through the LED, the brighter the LED will shine. Also, as the current passing through each LED increases, the heat produced by each LED generally increases. Exposure to high or constantly changing heat levels may affect how long an LED will remain operational and reduces efficacy.
In order to control the current flowing through each LED, it is known in the art to place a resistor in series with the LED circuit. While the resistor will provide some current protection in the circuit, it will not prevent the current from reaching higher levels if an increased amount of voltage is applied to the circuit. A resistor will also waste energy and raise heat levels within the circuit. As the voltage applied to the circuit ultimately increases, so will the current and heat within the circuit.
Therefore, it would be advantageous to design a circuit, device, or system utilizing LEDs that limits and controls the current in an LED circuit.
It would also be advantageous to design a circuit, device, or system where AC LED circuits may be used with DC power in a manner which may extend device or system life.
The present invention is provided to solve these and other issues.